Bill Gross may have just opened the floodgates. Still, Allianz, the German insurer that owns fund house Pimco, isn't likely to be swamped by his departure.

Mr. Gross, the mercurial founder and star fund manager at Pacific Investment Management Co., is off to join rival Janus in a huff. So the outlook for assets in the $222 billion Pimco Total Return fund he has managed for decades is in doubt.